Research On The Temperature Stress Response Mechanism And Genetic Relationship Of Taraxacum Officinale F.H.Wigg.

The chinese medicinal materials dandelion is the dried whole grasses of Taraxacum mongolicum Hand.Mazz.,Taraxacum borealisinense Kitam.,or several same genus plants.There are many types,which has the function of heat-clearing and detoxifying.What’s more,the economic utilization value is extremely high,and the demand is increasing year by year.Taraxacum.officinale F.H.Wigg.is the mainly cultivated species of chinese medicinal material dandelion.Taraxacum.officinale F.H.Wigg.not only has the extremely high ornamental value,but also have the effects of medicine while is an edible plan Taraxacum.Taraxacum.officinale F.H.Wigg.is greatly affected by temperature,such as "spring frost following warm spell" and summer high temperatures,which directly affect its yield and quality.In addition,Taraxacum.F.H.Wigg plants have similar morphological characteristics,and it is difficult to divide the interspecies.The mature plant of Taraxacum.officinale F.H.Wigg.cannot be identified from the existing classification points.Taraxacum.officinale F.H.Wigg.“Mingxian I”seedlings were treated for low temperature stress(4℃)and heat stress(38℃)experiments to investigate the physiological response and related response genes expression under temperature stress,and to perform gene cloning and bioinformatics analysis on key genes for temperature response,laying a foundation for the analysis of temperature response.The phylogenetic relationship of Taraxacum.F.H.Wigg.plants were studied to provide a basis for germplasm identification of Taraxacum.officinale F.H.Wigg..The results in the study are showing as follows:1.Taraxacum.officinale F.H.Wigg.seedlings were treated with temperature stress at different time.The results showed that seedling morphology significant changes in Taraxacum.officinale F.H.Wigg.under temperature stress,it is characterized by leaf color chlorosis,leaf margin curl,plant wilting,etc.The leaves submicroscopic structure of Taraxacum.officinale F.H.Wigg.seedings were damaged obviously,manifested as the double-layer membrane structure appeared in the cytoplasm,the number of starch grain and mitochondrion increased,and the cytoplasmic separation was obvious.Under high and low temperature stress,the POD activity,CATactivity,ETR and NPQ all firstly raised and then decreased;F_v / F_o,F_v / F_m,ΦPSII overall attenuated;and the content of MDA relative electrolyte conductivity increased.What’s more,SOD and proline showed overall attenuated,and Fo firstly increased and then decreased under low temperature stress.However,SOD decreased volatility,the accumulation of proline first increased and then fall down,Fo decrease at firstly,and then increased under heat stress.The results showed that Taraxacum.officinale F.H.Wigg.seedlings couldn’t normal growth under temperature stress,the photosynthetic capacity of leaf decreased and the biofilm systems damaged,nevertheless,it can alleviate the temperature damage by increasing the activity of protective enzymes and accumulating proline,which contribute to enhancemen to emperature resistance.2.Researching the related response genes expression level of Taraxacum.officinale F.H.Wigg.under temperature stress using RT-qPCR and three kinds of software,18 S and GAPDH were screened as the optimal reference genes.3.The temperature-responsive gene expression level of Taraxacum.officinale F.H.Wigg.by used RT-qPCR technology under temperature stress.The results showed that,the expression levels of AP2 / ERF,HSF,Glos,HSP,NAC,XCT were firstly up-regulated and then down-regulated during low and high temperature stress.Changs of b ZIP and NTL6 were undulant under temperature stress.Dof,ICE1 and MYB were firstly up-regulated and then down-regulated under low temperature stress,but down-regulated continuously under high temperature.The expression of WRKY under high temperature stress was much higher than that under low temperature stress.Based on the genes expression,it was speculated that the response mechanism of Taraxacum.officinale F.H.Wigg.were different under low temperature and high temperature stress.AP2 / ERF and Dof mainly respond to low temperature stress,and HSF,XCT and WRKY mainly played a role in high temperature stress.The key temperature responsive genes of Taraxacum.officinale F.H.Wigg.were cloning and bioinformatics analysis.Obtain the full-length CDS sequence of 5genes.The results showed that 5 temperature-responsive genes encoding proteins were all hydrophilic proteins,phosphorylation sites were all serine > threonine > tyrosine,which had different physical and chemical characteristics,subcellular localization,secondary structure,and tertiary structure.To_Dof protein subcellular localization predicted was outside the cell,To_HSF was in the cytoplasm,and the other three proteins were localized in the nucleus.Phylogenetic analysis showed that genetic relationship between To_AP2 / ERF protein has high similarity with Oryza sativa L.AP2 / ERF protein;To_Dof protein has high similarity with Helianthus annuus L.Dof protein;To_HSF has high similarity with Hevea brasiliensis(Willd.ex A.Juss.)Muell.Arg HSF protein;To_XCT has high similarity with Lactuca sativa Linn.XCT protein;To_WRKY protein has high similarity with Capsicum annuum L.WRKY.4.In order to explore the genetic relationship between Taraxacum.officinale F.H.Wigg.and other Taraxacum.F.H.Wigg.plants,13 species of T.F.H.Wigg.karyotype parameters were analyzed by karyotype approximate coefficient cluster analysis method.The result shows that the degree of evolution of Taraxacum.officinale F.H.Wigg.was lower than that of other Taraxacum.F.H.Wigg.plants.The phylogenetic relationship between Taraxacum.officinale F.H.Wigg.and Taraxacum.mongolicum Hand.-Mazz.was closest,resemblance-near coefficient was 0.7557,and the karyotype evolutionary distance was shortest,which was 0.2801.13 Taraxacum.F.H.Wigg.species were clustered into four groups when the karyotype near-coefficient was close to 0.6960.However,when it was close to 0.4641,13 species of dandelion were classfied into one group.Among them,the phylogenetic relationship between Taraxacum.heterolepis Nakai and Taraxacum.asiaticum var.lonchophyllum was closest,resemblance-near coefficient was 0.9969,and the karyotype evolutionary distance was shortes Taraxacum.What’s more,phylogenetic relationship between Taraxacum.dissectum(Ledeb.)Ledeb and Taraxacum.Asiaticum Dahlst was farthest,resemblance-near coefficient was 0.3343,and the karyotype evolutionary distance was farthes Taraxacum.